This is an old one that people should know. Basically, it's saying people only buy after a sales pitch goes to them 7 times (something similar to that). Anyway, the ways of incorporating this method are often email and social media.
Yes, I've heard this quite often. The first time you hear about the new Hamburger at McDonald's, you don't go out and try it. But after you've seen the commercial or heard it talked about or whatever a multiple number of times, that's when it sticks in your brain and you're most likely to try it. Consumers need repeated exposure to sales pitch in order to make a purchase.